In recent years, the development has increasingly been made on next-generation optical interconnect technology using integrated optical devices that are fabricated using silicon. In this technology, the optical devices such as an optical waveguide, a wavelength demultiplexer, and a light receiver which are fabricated using silicon are collectively integrated on one substrate.    Non-patent Document 1: Spector, S. et al., “Compact carrier injection based Mach-Zehnder modulator in silicon”, presented at the Integr. Photon. Nanophoton. Res. Appl. Conf., Salt Lake City, Utah, Paper ITuE5, 2007.    Non-patent Document 2: Gan, F. et al., “Compact, Low-Power, High-Speed Silicon Electro-Optic Modulator”, Conference on Lasers and Electro-Optics (CLEO), CTuQ6, 2007.    Non-patent Document 3: Baba, T. et al., “25−Gb/s broadband silicon modulator with 0.31−V·cm VπL based on forward-biased PIN diodes embedded with passive equalizer”, Optics Express, Vol. 23, Issue 26, pp. 32950-32960, 2015.